Four Methods to Remove Colorcast in Photoshop

Sometimes getting the color balance right on digital shots is difficult. Here are some techniques for using Photoshop to improve the color of your photographs.

Method One

The first method will be the short and sweet one.
With the image open add a levels adjustment layer above the background. We could make a copy of the background as a safety, but we are using an adjustment layer in this case. When the levels dialog opens, go under each color channel and pinch in the shadow and highlight sliders so they are placed where the information begins in the histogram view of the dialog. That’s it! Done

Method Two

Before starting the next method, make sure that the eyedropper tool is set for 3 by 3 or 5 by 5 and not to point. With the same file open, go under the adjustment layer icon at the bottom of the layers palette and select “threshold”. This will make the image black and white. Pull the slider all the way to the left, (this will turn the view entirely white) and start bring it slowly back to the right until black clusters appear. Bring the cursor over the image and it turns into the eyedropper.

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Place it over the cluster and click to add a point to the shadow area. Now move the slider all the way to the right (this turns everything black) and start bringing it back to the left until white clusters appear. Place a point to reference the highlight point of the image. The reason we look for a cluster is for better sampling consistency. Be careful not to select points in the image that are spectacular highlights.

Click “cancel” as we no longer need the threshold adjustment layer. You should see the 2 point added to the image, if you have not selected the point sampler tool (eyedropper) from the tool palette. With the 2 points visible, add a levels or curves adjustment layer. Double-click on the shadow eyedropper to identify the brightness range. Set the brightness to 4%. Double-click on the highlight eyedropper and set the brightness to 96%. This will ensure the point will have detail. Now simply use the shadow eyedropper to click on the shadow point and the highlight eyedropper to the highlight point.

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Photoshop will ask you if you wish to keep the new settings as the defaults. You can choose to do so if you desire or have Photoshop revert to the original settings as the default.

Method Three

This method involves identifying middle gray. Add a blank layer above the background layer and fill it with 50% gray – Edit>Fill>50% gray. Put this layer into “difference” blend mode. This will display anything that is 50% gray as the darkest parts of the image. Since we need to identify the darkest parts of the image, using a “threshold” adjustment layer makes the most sense. Bring this up through the layers palette, with the adjustment layer icon. Move the slider all the way to the left (turning the image totally white). Now bring the slider up slowly to the right until you get a cluster of black to show. Add a point of reference here as “middle gray”.

Essentially, the threshold layer identified the darkest part of the image below, which in fact would be 50% gray because of the fill layer in difference mode.
Cancel the threshold dialog and you can move the 50% gray layer to the trash if you like as we are finished with them. Using a curves or levels adjustment layer, this time select the middle eyedropper as the sampler and click on the new point.

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Method Four

The final method uses a color check card as a reference point. It is recommended that using these cards is the most accurate way of reducing the introduction and removing colorcast artifacts from the image.

Place 3 sample points on this image 1=black box, 2=white box, 3= gray box. Take note of the information in the info palette, as this is what will be referenced in this lesson.

Add a levels adjustment layer to the layer stack. Observe the info palette and look at point 1 (black); take the lowest of the 3 numbers you see. The goal will be to make all color channels the same. Go to the individual color channels in the levels dialog and click once in the input box for the shadows. Using the up arrow, click on the channels that need adjusting so they all equal the lowest original value. There will be 2 numbers referenced in the info palette, the first is the original and second is where it is moving.

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Once you’re complete with the black point, move to point #2 (white), click in the far right box and use the down arrow to adjust the individual channels so they equal the original highest value. This will complete the black and white points.

Next, add a curves adjustment layer to the stack. Look at point #3 in the info palette, take the average of the 3 channels by adding them together and dividing by 3. This is the value to move each channel to. Select the red channel and Option-click in the curves dialog to maximize the grid. Add a point to the bottom of the curve one section up to anchor the already established black point. Do the same to the top of the curve to anchor the white point. Finally, add a point to the middle of the curve and look for the input and output boxes at the bottom of the dialog. Enter the original red channel value in the input box and the value to change to in the output. Repeat this for all 3 channels and click OK.
This will adjust the mid-tones and complete the correction.

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Founded in 2005, Layers Magazine is one of the web’s premiere destinations for photographers, filmmakers, designers, and other artists who are interested in how new creative tools and techniques are being used in the industry today.